To study the last few millennia—younger than ancient rocks, but older than direct scientific monitoring—scientists can measure magnetic orientations in certain archaeological artifacts. But this record is heavily biased toward the north. More than 90 percent of the data about the last 2,000 years of Earth’s magnetic field come from above the Equator.

To track the South Atlantic Anomaly, researchers are searching for more sites in the Southern Hemisphere. In 2015, scientists announced a fascinating new data source: burned huts in the Limpopo River Valley, an area that falls within modern-day Botswana, South Africa, and Zimbabwe.

Iron Age peoples of southern Africa burned their structures periodically, with fires hot enough to preserve the floors as durable clay. It’s remarkable that literally the floors beneath the feet of ancient people are connected to the dynamics deep within the Earth, and our protection from the stars.

John Hawks is the Vilas-Borghesi Distinguished Achievement Professor of Anthropology at the University of Wisconsin—Madison. I work on the fossil and genetic record of human evolution (About me).

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